Flyback converters are generally known. For example, the topology of a traditional flyback converter can be seen in FIG. 1, and includes a transformer with a primary and secondary winding, and an output capacitor that supplies energy to a load. The primary winding of the transformer is directly connected to the input voltage source when the switch S is on, which causes an increase in the current and magnetic flux in the transformer and results in energy storage by the transformer. This also induces a negative voltage in the secondary winding. In this mode, the voltage stress across the transformer is Vin.
When the switch S is off, the energy stored in the transformer is transferred to the output of the converter. In this mode, the voltage stress across the switch S is Vin+N1·Vout/N2, and the voltage stress across the transformer is N1·Vout/N2.
Even though the flyback converter circuit of FIG. 1 is simple, it has a number of disadvantages. For example, high voltage stresses are placed on the components; the transformer has a high turns ratio; and there is unidirectional transformer flux, which not only results in large core size, but can also easily lead to core saturation. Furthermore, an additional snubber circuit is required to deal with transformer leakage inductance. DC offset current in the mutual inductance of the transformer also causes transformer core loss that cannot be reduced.
For at least these reasons, there is a need for an improved flyback converter. Embodiments of such improved flyback converters are contemplated by the invention, and various examples thereof are illustrated and described herein.